Brass Soldering Techniques

[knewsom]

I have a Tenshodo USRA 0-8-0 that I am attempting to fix.  The light on the tender had come off, and I am having a hard time getting it soldered back on.  I have both a 30 watt pencil soldering iron and a 125/250 watt soldering gun.  The light casting on this model is actually 2 pieces, a base and then a round casting for the light housing.  I have been able to get the light housing attached to the base with the pencil iron, but when I try to attach the base to the tender I can not get it to solder properly with the pencil iron.  So I tried to use the gun, too much heat was generated and the light housing came loose from the base.

Does anyone have any suggestions as to how this can be done, without the purchase of a resistance soldering station?

 

[BigRusty]

My friend Charlie was an artist at superdetailing brass. He used a resistance solderer because he said there is no way to add small parts to brass with a soldering iron. If you can find a way to heat sink the bottom joint and then quickly do the upper part it might work. If the light doesn't have to be grounded, you could use ACC.

[Johnnny_reb]

You could try an old technique used in auto body work when they used lead. Make a small dam with damp putty around the spot to be soldered, the putty should act like a dam stopping the brass around the spot from drawing up the heat while letting you get enough heat into the area to do your soldering. I would start with the largest piece and work toward the smallest. Stopping along the way to let it cool off completely before moving on to the next piece. Size has a lot to do with having enough heat into the part to solder and the larger a piece is the more heat it needs.

What happens is once you get enough heat into the larger piece to solder it to the tender body it has too much heat for the smaller light casting so that solder joint melts. But use the big soldering gun as the faster you get the heat in the better.

This is going to be like a dance with a fat lady (pardon the pun) but you will have to put in just the right amount of heat to make the solder flow and NOT anymore then that or the joint will fail. Watching the old-timers work lead is like watching "Michael Angelo" paint, its an art.

[Arjay1969]

Not to sound like an intelligent donkey here, but if you don't want to buy a resistance soldering unit, borrow one.

Seriously, I've had to do brass repairs before, and a regular soldering iron doesn't get the heat to where you need it quickly enough to avoid melting other joints.  You COULD try CA or Epoxy, but  if the part has to have electrical continuity with the rest of the piece, you'd be very effectively insulating it.  Glues also tend to be weaker on metal-to-metal joints unless there's a large surface area involved.

 

Good luck! 

[nedthomas]

A pinpoint gas torch will also work. High heat for a short period of time. Here again you have a large investment in something you may not use often.

[knewsom]

Well I came up with a solution.  I soldered the parts in a different order this time and I got it to work.  I soldered the light base to the tender deck first with the soldering gun, then soldered the light casting to the base with the pencil iron.   It took me a few tries, but I got it to work.

I will get a resistance soldering station soon, but I need to wait until after tax season.

 

[SteamFreak]

You could also have used a small alligator clip with low spring tension as a heat sink, or even as a clamp to keep the light assembly together while soldering it to the tender.

[2-8-8-0]

Where would one get a "resistance soldering iron" is this something the local radio shack would have? Im in the middle of building some brass engines and would love a better method than the iron i am currently using.